The present invention relates to a cleaning composition to be used for cleaning oil-based paint from brushes and other tools such as rollers and sponges that have been used to apply said oil-based paint. The method of cleaning of oil-based paint from paintbrushes and painting tools has until now been done by soaking the brushes or tools in a solvent such as mineral spirits or turpentine. While this method effectively cleans the brush or painting tool it has serious environmental, health and safety drawbacks. The solvents used for this purpose are generally flammable creating a serious fire hazard. Secondly, they are also volatile organic compounds which quickly evaporate and contribute to hydrocarbon pollution of the atmosphere and resultant high ground level ozone concentrations. Thirdly, they are health hazards which can cause injury to internal organs due to inhalation and can cause dermatitis due to contact with the skin. Fourthly they are inconvenient to use and difficult to dispose of properly. Patents have been issued for safer paint brush cleaners but none so far have enjoyed commercial success.
U.S. Pat. No. 4,606,840 describes a composition containing hydrocarbons or chlorohydrocarbons, ketone, glycol, alcohols and/or other solvents, and a liquid surfactant and cosurfactant in a formulation containing water that is useful in cleaning paint from brushes and allows the cleaning to be finished off in water. The formulation described by this patent contains a high concentration of hazardous chemicals that could represent a health hazard to the user of the formulation as well as a danger to the environment.
U.S. Pat. No. 4,812,255 describes a paint remover for uncured paint containing organic carboxylic acid, N-methyl-2-pyrrolidone (NMP) and an alkylene glycol ether. This formulation is expensive and contains a high percentage of corrosive acids.
U.S. Pat. No. 5,098,592 describes a formulation for removing varnish and paint from wood or metal which comprises activating NMP and/or BLO with about 1-30% by weight of an activated compound which is ethyl 3-ethoxypropionate (EEP). This paint remover would be prohibitively expensive for use in cleaning uncured paint from brushes and tools.
U.S. Pat. No. 4,251,383 describes a cleaning liquid containing an essential oil (eucalyptus oil), a softening agent (a fixed oil derivative such as coconut oil diethanolamide), and surfactants. It is stated that the formulation is useful in removing soil, stains, varnishes and the like from various surfaces and natural fibers. It appears that this formulation is designed for removing stains and not for removing large amounts of paints from paintbrushes. In any case the use of large amounts (50-70 %) of eucalyptus oil or other essential oil will render the formulation prohibitively expensive for cleaning paintbrushes.
U.S. Pat. No. 5,104,567 describes the use of a blend of 90-99% vegetable oil (in particular soy oil) and 1-10% of a surfactant emulsifier for cleaning ink from machine parts and rubber sheets in the printing industry. The cleaning process can be finished off with water. I have shown through experimentation that more than 10% surfactant is required to remove paint from paint brushes in a fashion that allows them to be finished up with water. At surfactant levels of 10% or below, partial removal of paint from the paintbrush will occur but a significant amount of paint will remain in the brush when the brush is washed with water. This residual paint will adhere tightly and will not wash out with subsequent treatment with the paint brush cleaner. Many patented and commercial paint removers are intended for removing both cured and uncured paint from surfaces and brushes and as such contain aggressive cleaning agents such as ketones, chlorocarbons, N-methyl-2-pyrrolidone, methylene chloride and other chemical substances. Such aggressive cleaning methods are not necessary for normal cleaning of oil-based paint from paint brushes. The paint that remains in paint brushes and other painting tools does not cure for a matter of hours after use allowing time for the brushes to be cleaned with a much less aggressive, inexpensive and safer cleaning liquid.